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Studies have found why older people and people with underlying conditions at particular risk have severe Covid-19.

Findings of the study

• While these risk groups produce greater quantities of the immune cell known as ‘T-helper cells’, their T-helper cells show impaired function.
• Advancing age and overall comorbidity scores were linked to a decrease in the proportion of cells producing an important messenger molecule.
• This stimulates other components of the immune response. In patients with risk factors, some of the SARS-CoV-2-specific T cells no longer function properly.
• The researchers were able to show a correlation between the frequency of virus-specific T-helper cells and the patients’ age.
• The same positive correlation was also found in relation to the ‘Comorbidity Index’, a measure expressing the severity of 19 different underlying medical conditions. The higher the patient’s Comorbidity Index, the higher the number of SARS-CoV-2-specific T-helper cells in their blood.
• A protein called PD-1 is known to act as a molecular ‘brake’ on the immune system. It regulates the immune response so as to prevent the immune system attacking the body.
• The researchers showed that the virus-specific T-helper cells produced more PD-1 in patients with acute infection, than in those with milder symptoms.

Reference:

1. https://indianexpress.com/article/explained/in-high-risk-patients-study-shows-how-covid-impairs-immune-activity-6588491/